Still camera lens attachment



Oct. 9, 1962 A. S. MILINOWSKI, JR., ETAL STILL CAMERA LENS ATTACHMENTFiled July '7, 1960 2 Sheets-Sheet 1 lim Edward Eloyd de Cariky BYFe/)fwn Fsk Oct. 9, 1962 A. s. MlLlNowsKl, JR., ETAL 3,057,258

STILL CAMERA LENS ATTACHMENT 2 Sheets-Sheet 2 Filed July 7, 1960 f. 04Jv, f www W jmzrk OSafS W j Twcl.. N C 1 E0 F .LVMH- ,W 1.2% uw WLM M/ 27 S 9 ,.0 ndm/ l vri a@ a au Novlws T AEW HTTRNY STiiiji CAMERA LENSATTACEMENT Arthur S. Miiinowsiri, lr., Nerv/alli, and Edward L.

This invention relates to a still camera attachment usable in anairplane for the purpose of combining images from a sight reticle of thecross hair or concentric circle type and a gunnery practice target. Thatis, the invention is intended to combine the image of a reflex sightreticle and that of a plane which is to be shot down by practice fire,so that the actual guns are not fired, but where instead a picture or aseries of pictures of the target and the reticle are taken in order todetermine Whether or not the student gunner has in fact aligned thetarget and his gun.

During peace time there exists the problem of keeping military pilotsand gunners in practice as to shooting down what would be, in war-time,enemy planes. Of course, in peace time no such targets exist, and asubstitute means such as a camera must be used in place of the cannon ormachine guns which would normally be used in War-time in order toprovide the practice and the training necessary for the pilot and/ orgunner to become and stay proficient in shooting down enemy planes whenthe real occasion arises.

Generally a practice camera is used in such a manner that a picture ofthe target and the sight are taken in order to record what the actualrelationship of the target and the gunners or pilots sighting means Wereat the time the operator pulled the trigger of what would be in War-timean actual rocket tiring mechanism, cannon or machine-gun. Thus, a recordof Whether or not the operators firearm actually was on target, at thetime that he decided it Was in fact so, is preserved so that both bothhis instructors and superiors may determine his proliciency and also sothat the gunner or pilot himself may determine in What manner his firingis inaccurate.

In planes of the pursuit or tighter type, the usual sighting means is aso-called reex sight, that is, the type of sight in which the reticle isprojected at infinity indirectly into the eyes of the pilot, so that thepilot may see in the same plane, i.e., at optical infinity, both thetarget that he is firing at and the reticle of the sight. In such typeof planes the gunner is, of course, the pilot himself and the sole meansusually used for aligning the firearms of the pursuit plane and itstarget is reorientation of the Whole plane so that the planes axis ispointing at the target.

Since the pilots job in a fighter plane is then basically to align theaxis of his plane (and therefore the axis of the rockets, cannon ormachine-guns carried thereby) with the target, typically the type ofsight is a center reticle sight; that is, that type of sight which markseither by concentric circles or cross hairs, the center line or axis ofthe plane. Because this sight is of the reflex type, the actual reticleis not seen directly by the pilot but, on the contrary, is actuallyprojected into the pilots eyes through an optical system, of which thereticle is at the focal point, so that the reticle itself is seen as ifit were at optical infinity. When the axis of the plane as determined bythe center of this projected reticle and the target which the pilotintends to shoot-down are aligned, the pilot of course would normallyfire the rockets, machine gun or cannon mounted in his plane thus tobring down the enemy.

yIn order to adapt such a system to training and refresher practice typeof operation, a means must be provided to Cil 3,057,258 Patented Oct. 9,1962 combine the target and the reticle image in the same relationshipas normally seen by the pilot and to record these permanently on aphotographic film. Combining these images and keeping both the targetand reticle images in exactly the same optical and apparent spatialrelationship as they would appear to the pilot is a problem, which isdifficult to solve, since not only is precise optical alignment of thesight, camera and pilots line of vision required, but also because sucha system must be capable of withstanding the high inertial loadssustained by a modern pursuit plane in flight. That is, such a systemmust not only be optically true when it is installed, but it must remainso after repeated landings and take-off, or at least be capable ofadjustment to be once again accurate with only a reasonable amount ofmaintenance.

Further, such an apparatus must be quite small in order to fit into thealready cramped cockpit of a modern fighter plane of the jet type. Thepresent invention is directed to such an apparatus and accomplishes aspecific solution to an extremely difficult technical problem bycomparatively straight-forward and therefore easily adjustable opticalmeans. In accordance with the invention, an optical system having thegeneral properties of a telescopic periscope but of quite smalldimensions and an extremely high precision (as to alignment of theimages therein and to resolution ability of the optical system) isprovided for the purpose fully described above.

Although the specific system illustrated in the accompanying drawing anddescribed hereinafter in detail is intended for an F104 fighter plane,the invention is of course not limited to such a specific embodiment buton the contrary is only exemplified by the disclosed specific opticalsystem and mounting means therefor hereinafter fully disclosed. Thegeneral problem which the invention solves is rather the provision of anoptical system of high precision, which can combine very accurately andwith virtually no angular error, two images (i.e., the target and thereticle image) along a reference line (i.e., the pilots vision line)without obstructing the pilots view and Without impeding in any mannerthe operation of the reticle sight and further enabling a picture to bemade of the exact orientation of the rellex reticle sight and the targetat the time that the pilot decides he is in fact on target and thereforeshoots An object of the invention is therefore to provide a cameraattachment for combining the images from a reticle and from a target sothat a photograph of this combined field of view may be taken.

Another object of the invention is to provide a device of the above typewhich is very compact so that it does not interfere with the normal lineof View of the adjacently seated pilot.

A further object is the provision of a device having not only anaccurate optical system which is carefully aligned so that the reticleand target images are kept in the same relationship as they wereoriginally seen by the pilot, but also one which is comparatively strongmechanically so that the system does not go out of adjustment upon useand exposure to extreme inertial loads of acceleration and decelerationtype.

Another object of the invention is the provision of a device of theabove type which is not only small in those parts which interfere withthe pilots line of view but is also small in overall dimension, that is,does not occupy too much general space of the cockpit so that it doesnot interfere with the other controls of the cockpit or any part of thepilots body.

A further object of the invention is to provide a device of the typedescribed above in which there is an economy of optical elements,mechanical mounting means, and in which the number of precision partsnecessary to establish and maintain precise optical alignment of theenclosed parts is kept to a minimum, thereby making the manufacture andmaintenance of the instrument comparatively inexpensive for theprecision desired. Y

Other objects and advantages of the invention will be obvious to oneskilled in the art upon reading the fo-llowing specification and uponstudying the accompanying drawing, in which:

FIG. 1 is a side view, part elevational and part sectional, of thecamera attachment, also showing the general arrangement ofl the reflexsight assembly and the combining glass used for combining the imagethereof with the pilots line of View;

FIG. 2 is a rear elevational view of the attachment which forms thesubject matter of the invention;

FIG. 3 is a schematic optical diagram of the elements in the periscopetaken from the rear, i.e., looking in the same direction as the pilotwould be in the aeroplane in which it is used;

FIG. 4 is a plan schematic optical diagram of the optical system, thatis, looking down from the top of FIG. 3.

Although the invention is not limited by the specific embodiment shownand hereinafter described, nevertheless, in order to comply with thepatent statutes, a specific structural embodiment is shown and describedin detail.

Referring to FIGS. l and 2, the existing reflex reticle sight supports,by circular mounting flange 12 and mounting bracket 13, the cameraattachment generally shown at 14. The camera attachment generallycomprises a pri-sm mounting head assembly 16, an objective tube `18, andan elbow tube 20. Suitable attaching means,

such as screws 22, are used to attach these last two mentioned tubularassemblies together. Connected to the end of elbow tube 20, which isremote from objective rtube 18, is the second objective tube 24, whichin turn is connected to the camera lens tube 26. At the right- =hand endofthe camera tube 26 (see FIG. 2), the camera 200 used with theattachment is connectedr thereto such that the film plane -thereof liesbelow the extreme righthand end of said tube 26. Combining glass 30 isso arranged (see FIG. l) that the image reflected by reflex sight 10 isreflected by plate 30 into the left-hand surface 32 of prism headassembly 16. The light rays from the reticle follow the path 34 upward,are reflected from right side 36 of plate 30, and then follow the path38 to so reach the prism head assembly 16.

FIGURE 3 shows more clearly the path of light through the cameraattachment and shows the optical elemen-ts lcontained therein. No.attempt has been made to show the exact internal mounting of theseelements since any conventional means may be used.

The light entering the prism housing head |16 along path 38' isreflected by prism 40 such that it is deviated in a downward directionalong path 46 to first lens group 50 of the first objective lensassembly, thence to second lens group 60, and then to right-angle prism68. This right-angle prism reflects the light rays to the right as seenin FIG. 2 to the third group 70 of the second objective lens assembly,then to prism and lens assembly 150 (see FIGS. 3 and 4). This prism andlens assembly 150 is composed of prisms 154 and 172, first group 160 ofthe second objective lens, Petzval curve corrector 80, and third group90 of the second objective lens. The rays then enter the final prism andlens assembly 100 which is generally comprised of right-angle prism 100and the camera lens assembly 110.

In detail, the optical system generally just described is comprised asfollows. Prism 40 is of the single-reflecting type and its general shapeis best seen in FIG. l. The first group 50 of the first objective lensassembly is composed of double convex lens element 52, negative meniscuslens 54 cemented thereto, air space 56, and nearly plano-convex lens 58.The first objective Petzval curve corrector 60 is of little dioptricpower and is composed of first Petzval corrector 62, air space 64, andsecond 1 Petzval lens element 66. After being reflected by theright-angle prism 68, the rays encounter lens element 72 of the thirdgroup of the first objective 4lens assembly, pass therethrough and thenthrough air space 74, meniscus concave lens element 76 and then doubleconvex lens 78.

The rays then enter the lefthand surface 152 of Abbe prism 154, arereflected upward (see FIG. 3) by surface 153 along line 155 and thenstrike surface 156. This surface 156 is angled (at 45 to the plane ofthe paper in FIG. 3 in such rela-tionship as to reflect verticle rays155 directly into the plane of the paper as seen in FIG. 3 (andtherefore apparently upward in the plan view of FIG. 4). The rays thenencounter the first element 162 of the rst group 160 of the secondobjective lens assembly (see FIG. 4).

After passing through the first double convex element 162 of said firstgroup, the rays then pass through the second element, concave meniscuslens 164, air space 166, and then the third and last element, almostplano-convex element 168 of said first group 160 of the secondobjective. Emerging from this group, the rays are reflected byright-angle prism 174 to the second Petzval curve corrector 80, which iscomprised of rst Petzval element 84, air space 86, and second Petzvalelement 88. The rays then encounter the third group of the secondobjective assembly, which comprises plano-convex lens 92, air space 94,and a doublet consisting of a negative meniscus lens element 96 andthedouble convex last element 98.

The rays emerging from this second objective lens assembly are thenrefiected by right-angle prism to the final lens assembly 110, whichacts as the objective lens of the camera 200, see FIG. 2. The cameraobjective is composed of first plano-convex lens 102, large air space104, double concave lens element 106 and, separated therefrom by airspace 107, plano-convex lens 108. The diaphragm of the camera lensitself is schematically shown at and actually passes 4through air space107; and the film plane, which of course has the final image projectedthereon by the optical system, is shown sche,- matically at 130.

The general koperation of the system will now be explained.Referring-back to FIG. 2, the operator of the pursuit airplane, i.e.,the pilot, sits with his eyes essentially level (in the horizontalplane) with the left top of the camera attachment (that is, in theneighborhood of the prism head assembly 16; but, of course, with one eyet'o the left and one eye to the right of the prism head). In thisposition, the pilot will see the target through the `combining glassplate 36 and at the same time will see projected upon this combiningglass an image of the reticle of the reflex sight. At such time as theoperator believes that the project reticle and the target are lined up,he will press a trigger (which would in war-time fire a rocket, a cannonor a set of machine guns). In training the effect of firing this triggeris only to take the picture of the scene seen by the pilot at the timethat he decided that he should fire The above-described attachmentaccomplishes the purpose of bringing to the film plane in the cameraboth the -imagesy of the target and the image of the projected reflex4sight reticle as seen by the pilot at the exact time that the pilotconsidered himself ina position to make a kilL As previously explained,the manner of accomplishing this purpose is -to unite, by means of thecombining glass 36, the reticle of the reflex sight projected along line34 (sce FIG. l) and then along line 38 into the camera attachmentproper. Since the optical system must keep both the reflected reticleimage and `the. more direct image ofv the target (iLe., the enemy plane)always coincident, the optical system must not only be aligned with `thepilots normal line of view but also must be so designed that itmaintains this relationship despite relatively high inertia-l loadsimpressed upon the camera attachment by the acceleration andIdeceleration of the plane.

This is accomplished by the invention as will be explained below inconnection with the operation of the optical system itself.

In FIG. 1, the reflex sight 10, projects as parallel rays 34 (i.e., atoptical infinity) an image of the reticle, which is then reflected bycombining glass 3ft into the prism head 16 through window 32. Theseparallel rays are reected by the single-reliecting surface 42 of prism4t) to emerge at the lower face of the prism along path 46. Theseparallel rays then encounter and are converged by the first group of thefirst objective lens (i.e., lens elements 52, 54 and 58 and air space56) to a focus at the first image plane Il. The first Petzval correctorelement 62 assists in making the Petzval sum of the first half of thefirst lens assembly (i.e., lens group 50 and corrector 62) a minimum,thereby making the lens anastigmatic, i.e., yielding a fiat-field image.

This image of the reticle, I1, is at the first focal point of the thirdgroup 7l) of the first objective lens assembly, taking into account theeffect of the second Petzval corrector 66. In other words, lens elements66, 72, 76 and 78 and air space 74 are of such curvatures and spacingthat the image formed at I1 is at the focal point of this part of thelens system. Therefore the light emerging from the right-hand surface(see FIG. 3) of the last element 7S is parallel once more. It should benoted that the right-angle prism 68, although of course deviating thelight rays 9() degrees, does not affect in any substantial manner thedioptric effect of the second Petzval element and the third group of thefirst objective lens assembly.

rThe parallel rays emerging from last element 78 then enter left-haldsurface 152 of Abbe prism 154, are refiected upwardly by surface 153thereof to strike surface 156 so that the rays then travel into thepaper as seen in FIG. 3. These parallel rays, now traveling along line157 in FIG. 4 are then converged by the first group (elements 162, 164and 16S and air space 166) of the second lens assembly and strike therefiecting surface 172 of the right-angle prism 174, thereby beingreflected to the right (as seen at FIG. 4). The rays are slightlyrefracted as they pass through the first Petzval curve corrector element84, and come to a focus in the second image plane I2.

As in the case with the second half of the first objective system, thesecond half of the second objective system is also so positionedrelative to image plane I2 that the rays eventually emerging from thelast element of this half-lens system are also parallel. In other words,the image plan-e I2 is at the first focal plane of the combined opticalelements 88, 92, 96 and 98, including air space 94. The parallel raysfinally emerging from the right-hand surface of the last lens element 98are parallel as they enter right-angle prism 100 (see FIG. 3). Theseparallel rays carrying the image of the refiex sight reticle are thenfinally focused onto the film plane 130 by means of the camera objectivelens assembly 110. Therefore, the focal point of this camera objective,composed of lens elements 102, 106, and 10S and air space 104,previously described, coincides with the film at the film plane 130.

Thus a permanent photographic image of the reticle is placed upon thefilm in the camera by means of the optical system of invention.

The two objective lens assemblies are quite similar, and each is almostsymmetrical through its respective image planes, Il and I2. In fact, thefirst lens system (groups 50, 60, and 70) has a magnification power ofunity (and is perfectly symmetrical), although the second lens assembly(groups 16), 180 and 196) has a magnification power of 1.4 and is,therefore, obviously not symmetrical. Therefore, the number of differenttypes of lens elements (and lens groups) needed to be manufactured iskept to a minimum.

Since the optical path of the image rays from the target (i.e.,the/enemy plane) is substantially the same as that of the reticle of thereflex sight, such path will not be described in detail, but rather onlythe differences between the two paths are hereinafter described.Entering light rays 32', carrying an image of the enemy plane, enter thecockpit of the fighter plane and encounter first left-hand surface 35 ofthe combining glass 3f). The rays 32', though slightlyy refracted bythis surface 35, proceed in a slightly deviated straight line 33 throughthe glass and out the right-hand side 36 of the combining glass plate asrays 37, optically aligned with the rays 38 from the reticle sight whichhave been reflected by the same right-hand surface 36. Since the targetis, of course, at a great distance away from the combining glass, theenemy plane is in effect an optical infinity so that the light rays fromboth the reticle of the reflex sight and the target are parallel andtherefore are treated by the rest of the optical system (to the right ofthe combining glass) in the same manner, both in alignment and indioptric convergence.

The disclosed camera attachment therefore makes it possible to alignboth of these images in an optically true manner without any unnecessaryelements, adjustments, or mechanical complications. The sole opticaladjustments are accomplished by having the first single-reflectingsurface prism 46 mounted in an adjustable manner. In order to accomplishvertical or elevation adjustment, adjustment plate 182 which determinesthe angular position of the prism 40 is pivotally mounted about axis184; and adjustment screws 186, 188 are provided for pivoting thisplate. By tightening one of the adjustment screws and loosening theother, the prism 4f! is thereby rotated by a small, precise amount aboutaxis 184 (i.e., perpendicular to the paper in FIG. l) thus enabling theinstallation and adjustment of the camera attachment. This adjustmentcenters the optical axis of the rest of the optical system with theimages of the target and the reflex sight reticle in the vertical plane.Similarly, should the mechanical elements of the system become dislodgedbecause of vibration or inertial loads, caused by the operation of theplane or other causes, the prism adjustment enables the maintenance crewto re-adjust the system so that the target and the reticle sight imagesare once again made to coincide with the optical axis of the wholecamera attachment.

In order to enable adjustment of the line of sight in the horizontalplane (see FIGS. l and 2), the prism head assembly is preferably mountedso that it is rotatably adjustable about a Vertical axis. Therefore,prism head assembly 16 is rotatable with respect to first objective tube18 about the vertical aXis thereof. Since it is, of course, necessary tomaintain the prism head in one specific position, once the initialadjustment has been made, set screw (see FIG. 2) is provided to clampthe prism head firmly in the correct position about this vertical axis.

The initial adjustment of the correct sight picture to be seen by thepilot is made by slight rotation of the combining glass 30 about itscenter along a horizontal axis perpendicular to the plane of the paperin FIG. l. The effect of such rotation is to deviate through an angle,twice that of the rotation, the reticle rays 38 which have beenreflected thereby; but this rotation displaces the target rays 33, 37only a slight amount. Therefore, the reflex sight reticle image (see ray38) can be reoriented so that it precisely represents the axis of thefirearms intended to be used therewith, without this substantiallychanging the position of the target image. For this adjustment, means(not shown) similar to that used to pivotably mount prism 40 areutilized.

Since both mechanical rigidity and optical alignment are important, infact, crucial, to the operation of the entire system, circular mountingflange 12 is so shaped as to make good mechanical contact with the topof the reticle sight 10. (See FIG. 1.) Further, mounting bracket 13 isprovided with a large number of attaching screws, arranged in groups192, 194 and 198. As

eresmas shown in FIG. 2, the camera 200 is also firmly mounted to thecamera attachment, thereby affecting a good mechanical connection andthus a true optical alignment. Screw 202 (FIG. 2) and screw 214 areventing port cover screws. In order to firmly attach the elbow part ofthe mounting tube of the camera attachment to stationary parts of thecockpit of the airplane, a second mounting bracket 210 (see FIG. l)provided with attaching bolts 212 are provided at the. lower part ofthis elbow tube 20. Set screw 214 (see FIG. 2) is provided to hold tubes18 and 20 firmly together, as do screws 220 with respect to tubes 24 and26.

The invention therefore accomplishes the` desired results set out in theabove objects, of providing a strong, precise, comparatively easilymanufactured, and readily adjusted optical instrument for relaying theimages (as seen by the pilot) of the reticle in the reflex sight and thetarget onto a photographic film; and this is accomplished without anyunnecessary waste of space in the cramped quarters of the modern pursuitplane cockpit. Further, no interference with the pilots normal sight iscaused by use of this device.

Of course, a motion picture camera (with a similar lens) may besubstituted for the still camera box (200) and lens (110) disclosed,especially since the camera lens is really not a part of attachmentitself. Similarly other changes and modifications of the disclosedembodiment will be obvious to one skilled in the art upon seeing thisdisclosure, and this patent is intended to encompass all such changes.Therefore, the invention is not limited to the disclosed embodiment, butrather is defined in the appended claims and their equivalents.

We claim:

1. A camera attachment for relaying at least one image from at least onedistant object to a remotely located film plane inside a light-tightstill camera box, comprising:

a first reecting element 40 positioned so as to receive and redirect theparallel rays emanating from such distant object, said received andredirected rays determining a first plane;

a first achromatic positive lens group 50 in said redirected parallelrays for focusing said parallel rays t a first image at a rst imageplane I1;

a first Petzval curve corrector element 62 positioned between said firstgroup and said first image, for reducing the Petzval sum of said firstlens group, to thereby render said image flat at said image plane;

a secondkPetzval curve corrector element 66 and a second positiveachromatic lens group 70 positioned on the side of said first imageremote from said first lens group, andv at such distance that said first"image is at the principal focal plane thereof, the rays from said imageplane thereby being rendered parallel once again;

both said first and second Petzval curve corrector elements, on the onehand, and said first and second lens groups, on the other hand, beingsymmetrically arranged about said first image plane and being identical;

a second reflecting element 68 positioned between said second Petzvalcurve corrector element and said second positive achromatic lens group,saidk second reflecting element being disposed to redirect the raysperpendicular to said first plane;

a third reflecting element 153 positioned to receive and redirect therays from the second positive achromatic lens group, said received andredirected rays from the third reflecting element determining a secondplane;

a fourth reflecting element 156 positioned to receive and redirect raysin a direction perpendicular to said second plane;

a third positive lens group 160l and a third Petzval corrector element84 positioned in the parallel rays emanating from said second positivegroup to focus said rays to a second image and to make said imageanastigmatic respectively;

a fourth Petzval corrector element 8S and a fourth positive lens grouppositioned with their focal point at said second image plane thereby torender again parallel the image carrying rays from said second image;

said third and fourth lens groups, on the one hand, and said third andfourth Petzval correctors, on the other hand, being symmetricallyarranged about the image plane;

and a camera objective lens positioned in the parallel rays emergingfrom said fourth lens group so that said rays are focused at a third andfinal real image at the film plane.

2. Apparatus as definedin claim 1 including first mount.- ing means forrigidly mounting the attachment to adjacent structural members andsecond mounting means for connecting the attachment to a camera to beused therewith.

Davies et al. May 5, 1959 Baker Aug. 18, 1959

